Definition The Nash Product [efr-PTAE]

Let \epsilon \in \mathbb {S}(X), \epsilon ' \in \mathbb {S}(Y) be selection relations. Their Nash product \epsilon \boxtimes \epsilon ' \in \mathbb {S}(X \otimes Y) is given by \{(x \otimes y, k) \mid \epsilon (x,k(1_X \otimes y)), \epsilon '(y, k(x \otimes 1_Y))\}